The present embodiments relate to gas turbine engines and, more particularly, to cooling channels used in actively cooled gas turbine engine components.
Modern gas turbine engines increasingly operate under higher temperatures to achieve improved overall engine performance. However, the temperatures at the turbine inlet and along the gas path within the turbine generally exceed the melting point of the materials from which the exposed turbine components are made. As a result, turbine gas path components must be actively cooled to prevent failure.
One conventional means of cooling turbine gas path components involves the use of internal component channels, which pass cooling air, extracted for example from the compressor, to the turbine gas path component. This cooling air is typically hundreds of degrees to even a thousand degrees colder than the gas path. For instance, a turbine blade outer air seal can be made to contain internal channels running circumferentially in the engine through which cooling air is passed. The effectiveness of the channels ultimately dictates the temperature of the gas path component, and therefore, its ability to withstand modern gas turbine engine operating temperatures. Channel effectiveness can be increased by shrinking channel volume, and thus increasing flow speeds through the channel. Yet, the ability to shrink channel volume is limited due to the process capabilities of traditional manufacturing castings.
Additive manufacturing techniques can be utilized to overcome the limitations inherent in traditional manufacturing and increase the design space of cooled components. Additively manufactured parts are typically made by fusing successive powder layers to form the component. However, when an internal channel with an overhanging structure is additively built, the overhanging structure tends to collapse as additional layers of the component are built on top of the overhanging structure. Channel collapsing reduces the channel's cooling performance and can render the channel useless. To prevent channel collapsing, support material, such as loosely fused powder, has been used inside the channel. The use of support material inside a channel is problematic for microchannels where there generally is no access for cleaning the support material out from the microchannel after the build, leaving support material trapped inside the microchannel. This then also renders the channel useless.